Bees: Protect Your Pollinators

Bumblebees use their long tongues to feed on the flower nectar of fruit and garden crops, and their fuzzy hair picks up and distributes pollen.Photo courtesy David Green

Left: When berries are not fully pollinated by bees, small and malformed fruit often is the result. Right: Bees have successfully pollinated this berry.Photo courtesy David Green

This well-made nesting box for orchard mason bees from www.beediverse.com) features cleanable stacking trays and a green predator guard to preven woodpeckers from eating the bee cocoons and larvae.

You’ll harvest more and bigger fruits and vegetables
if you have enough pollinating bees visiting your garden.
In some cases, better pollination even means faster
maturity and better flavor.

Cornell University researchers have found that bee-assisted
pollination of strawberries can increase fruit size up to
40 percent. Other crops that depend upon native bees for
pollination include tomatoes, peppers, eggplants, pumpkins,
squash and melons, plus most berries and tree fruits. But
heavy reliance on pesticides, loss of habitat and
monoculture crop systems have decimated pollinator
populations.

“Monoculture makes it impossible for any bee —
native or otherwise — to keep year-round populations
sufficient for pollination,” says David Green, who
maintains the native bee Web site www.pollinator.com.
“A modern orchard has such a flush of bloom in spring
that the pollination task is overwhelming. The rest of the
year, it’s starvation or even a toxic
environment.”

Besides avoiding pesticides, you can support native bee
populations by protecting natural areas on your property,
leaving field and road borders un-mowed to provide habitat
for ground-nesting bees, and planting or preserving stands
of native flowering plants (that the bees use for food) in
pastures and hedgerows. A diverse selection of flowering
plants and food crops ensures that pollinators have a
steady supply of nectar and pollen throughout the growing
season.

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Take a close look at the flowers in your garden and you
will quickly see that honeybees, which are native to
Europe, have plenty of company, including numerous native
bee species with specialized talents. But while honeybees
are commonly protected by a beekeeper, native bees have no
human guardians. This is why it’s important to help
build native bee populations in your own area.

Like honeybees, native bees feed on nectar while gathering
pollen to take back to their nests as food for their young.
In the process, they pollinate flowers, often doing a
better job than honeybees on certain crops such as apples,
berries, alfalfa and almonds. Bumblebees are the preferred
pollinators for greenhouse-grown tomatoes, and pumpkin
growers from Wisconsin to Alabama are recognizing the value
of squash bees — short-lived native species that
often outnumber honeybees visiting squash blossoms, even
when honeybee hives are nearby. In areas where cool
temperatures limit honeybee activity during the spring
blooming of fruit trees, native mason bees do the job
because they are better adapted to cool weather.

Pollination in some crops is a collective effort among
different species, however. Researchers at Ohio State
University found that 18 species of native bees were doing
most of the pollinating work in nearby strawberry fields.

These native bees don’t produce honey, and they
can’t be reared in managed hives. But when they are
given even small patches of suitable habitat, such as a
fence row or diverse garden, some of the 4,000-plus species
of native bees will show up.

“In a 20-acre woodland park that includes trees and
flowers and that hasn’t been sprayed with pesticides,
there may be 100 species of native bees present on a summer
day,” says Jim Cane, research entomologist at the
U.S. Department of Agriculture’s Bee Biology Lab in
Logan, Utah.

According to the National Sustainable Agriculture
Information Service, the following native bees are
particularly good pollinators of certain crops, although
they pollinate other flowering plants, as well:

It’s also important to understand that male bees
can’t sting (a bee stinger is a modified egg-laying
organ), and females won’t sting unless they are
provoked. “They have no honey to protect, so they are
not built to defend themselves from mammalian
predators,” Cane says. If you find that you like
sharing the company of native bees, or you want to enlist
their help to pollinate your plants, some species will
accept human invitations in the form of nesting boxes.

Wild Bee Lifestyles

Big, fuzzy, black-and-yellow bumblebees and a few types of
small sweat bees are the only native bees that live in
colonies. Most other species live alone and associate with
others only long enough to mate. Mason bees, carpenter bees
and leafcutter bees are called cavity nesters because they
make their nests in the holes of trees, fence posts,
firewood, hollow plant stems or handmade bee nesting
blocks. More numerous ground-dwelling bees dig tubular
burrows no larger than a drinking straw. Bumblebees often
make their home in underground burrows vacated by rodents.

Like honeybees, bumblebees are general feeders that visit a
broad range of host plants. But many wild bees have
restrictive tastes and stick close to the plants they were
born to serve. Squash bees, for example, followed early
strains of squash as native people moved the crop northward
from Central America. Females emerge in early summer and
only fly in the morning when squash blossoms are open. In
the afternoon, you often can find males curled up asleep in
closed squash flowers (yes, bees do sleep). Cane recently
worked with the specialist bee that pollinates only
rabbiteye blueberries — and that does so with amazing
efficiency. The adult life of a specialist bee is quite
short, but in only a few weeks, just one of them often
out-pollinates 100 honeybees.

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Because specialist bees need pollen from specific plants,
they tend to stay close to home and forage in smaller
plantings, says James Tew of Ohio State University’s
Honey Bee Lab. Most native bees pose no problem for plants,
though leafcutter bees do harvest rounded leaf pieces from
roses, ash trees and several other plants, which they use
to build their nests. “The small amount of leaf
material taken is a bargain when the pollination activities
of leafcutter bees are considered,” Tew says.

Various species of leafcutter bee have been found to be
much better pollinators of alfalfa, blueberries, carrots,
sunflowers and onions than honeybees. For example, in an
enclosed greenhouse where carrots were being grown for
seed, researchers found that 150 leafcutter bees could do
the work of 3,000 honeybees. One non-native species, the
alfalfa leafcutter bee, is now reared by the millions
because it does such an outstanding job pollinating alfalfa
grown for seed.

The Native Edge

Particular characteristics contribute to native bees’
pollination talents. Many native bees are quite hairy, and
tufts of hair (such as those on the abdomens of female
leafcutter bees) serve as soft brushes that gently transfer
pollen from a flower’s stamens to its stigma (the
female part that connects to the ovary). The buzz factor
also is important because some flowers, such as blueberries
and most members of the tomato family, need to be vibrated
to shake the pollen loose from the stamens. Scientists call
this process “sonication,” but Arizona
entomologist Stephen Buchmann (co-author of The Forgotten
Pollinators) came up with another phrase: “buzz
pollination.” Bumblebees, digger bees and several
other native bees are great buzz pollinators.

The diversity of native bees matches the diversity of
native plants. With the help of his camera, David Gordon, a
professor of zoology at Pittsburg State University in
Kansas, has seen that some native bees have long tongues,
so they can lap nectar from tubular flowers while others
have shorter tongues more suited to flat blossoms. Native
bees also vary in size from half-inch iridescent sweat bees
to 1½-inch carpenter bees. Tiny bees can access the
littlest flowers for pollination purposes while bigger bees
buzz blossoms, tramping pollen from place to place with
their feet, and sometimes accidentally improving
pollination by chasing honeybees across the faces of
sunflowers and other big-blossomed plants.

Enhancing Habitat

Native bees seldom travel more than a quarter mile from
their nests, so improving bee habitat can have a very
direct benefit in your garden. The Xerces Society, a
nonprofit insect preservation group based in Portland,
Ore., suggests several simple ways to make your property
more hospitable to native bees:

Minimize the use of pesticides and avoid
spraying botanical or biological insecticides in the
morning, when native bees are most active.
Grow a diverse selection of flowering plants
(including as many native species as possible).
Grow crops such as squash, sunflowers, blueberries
and strawberries every year to maintain resident
populations of the specialist bees that serve them.
Leave some areas uncultivated so you don’t
disturb bees that nest in the ground.

The same plants that attract butterflies and beneficial
insects often attract native bees; both insect groups are
most numerous where plants bloom over a long season. For
example, early spring-blooming willows and redbuds can be
followed by fruit trees, brambles and red clover before
your summer vegetables and flowers take over as primary
host plants. Then keep the pollen flowing into fall by
growing late-blooming asters and allowing goldenrod to
flourish along fence rows.

With a solid food supply nailed down, you can further
encourage native bees by providing attractive nesting
sites. For ground-nesting bees, a patch of uncultivated,
well-drained soil that gets morning sun will work well as
long as you avoid disturbing it with vehicles and tractors.
You also can make a sand pile or sand pit — or simply
fill a planter with sand and place it on a warm,
south-facing slope. If you see bumblebees buzzing around
the roots of a tree, leave them alone. They probably have
established a colony in a burrow vacated by mice or voles.

Beyond the benefits of improved crop pollination, good food
and habitat for native bees has a ripple effect in the
natural world. Native bees pollinate forest trees and
wildflowers, which in turn provide food for wildlife. Cane
says that because wild bees are vegetarians, they will
never ruin your barbeque by buzzing around your burgers.
“Sit down and enjoy the bees,” he suggests.
“They are great fun to watch.”

Barbara Pleasant is a veteran MOTHER EARTH NEWS contributing editor and award-winning book author. She lives in the mountains of western North Carolina.

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